[C++] Continuous loop until keypress?

[xsive]

I'm trying to loop a function continuously until a key is pressed (i'm implementing a manual/automatic run thing).
getch() is the closest thing I could find to help me achieve this but if i put getch() inside a loop the loop wont work unless theres some kind of input coming in.

All i end up with is a semi-automatic mode where the program loops while a key is held down. Surely there must be a better way?

[Geo]

Have you tried:

while ( cin.peek() == EOF ) {
         //do stuff
}

Might work...

[Jive Honky]

Hmm, maybe have the loop running in a separate thread and use a semaphore? Nah, screw that, too much work, just follow Geo's suggestion.

[xsive]

thanks guys

[Unregisturd]

Originally posted by Jive Honky
Hmm, maybe have the loop running in a separate thread and use a semaphore? Nah, screw that, too much work, just follow Geo's suggestion.

How would that work though? You'd still need something to check the keyboard and do an up on the semaphore, so you're still going to have something in tight loop...

[Jive Honky]

Originally posted by Unregisturd


How would that work though? You'd still need something to check the keyboard and do an up on the semaphore, so you're still going to have something in tight loop...

Well, I've only done multithreading in C, which is fairly easy, so I'm not sure how to do it in C++. My idea was to have a boolean called 'stop' which is set to false. So in the main thread thread you'd be continually looping until 'stop' is true.

while (!stop)
{
// do stuff
}

In a separate thread, it will just be waiting on input and will set 'stop' to true when it gets it.

cin >> stuff;
stop = true;

Or something.

[FlameHead]

Originally posted by Jive Honky


Well, I've only done multithreading in C, which is fairly easy, so I'm not sure how to do it in C++. My idea was to have a boolean called 'stop' which is set to false. So in the main thread thread you'd be continually looping until 'stop' is true.

while (!stop)
{
// do stuff
}

In a separate thread, it will just be waiting on input and will set 'stop' to true when it gets it.

cin >> stuff;
stop = true;

Or something.

That's how I would have done it. But if you wanted to break the loop where it was, id set the loop up in another thread, and when you press they key, an event or just straight input of somesort in the main, it would then teell the loop thread to stop.

But if that doesn't sound right, just ignore me since I only know Java well.

[volatile]

I don't know if this works in all C++ compilers, but I've used the _kbhit() function in Visual Studio C++ .NET a fair bit lately.

while (!_kbhit()) {
    //do stuff
}
char dummy = getch();

[Unregisturd]

Originally posted by Jive Honky
Well, I've only done multithreading in C, which is fairly easy, so I'm not sure how to do it in C++. My idea was to have a boolean called 'stop' which is set to false. So in the main thread thread you'd be continually looping until 'stop' is true.

Ok, after re-reading the initial post it would seem like threading is a good idea if the program is doing something else. But to check for a keypress, the other thread shouldn't need to loop - it will block waiting for input until it arrives.

[mertz]

char a;

while (1) {

if(cin<<a) { break; }

}

just use the return value from the cin object... but my syntax i wrong with the input object im sure.

[Jive Honky]

Originally posted by mertz
char a;

while (1) {

if(cin<<a) { break; }

}

just use the return value from the cin object... but my syntax i wrong with the input object im sure.

Unless I'm mistaken, the code will stop at the if(), waiting for input, instead of continuing, which is not what he wants (unless you have this in a separate thread, in which case why is it in a loop?).

EDIT: Welcome to the forums mertz.

Originally posted by Unregisturd
Ok, after re-reading the initial post it would seem like threading is a good idea if the program is doing something else. But to check for a keypress, the other thread shouldn't need to loop - it will block waiting for input until it arrives.

I'm not quite sure what you mean. The other thread isn't looping; it's just got a simple if() statement, and is stuck waiting for input, once it gets it the thread is finished and the loop in the main thread ends (because the condition is no longer true).

[Unregisturd]

I was just going off Geo's example... i'm sure there's a better way to do this, but I couldn't be bothered looking up my C/C++ and operating systems books.